The present invention relates to a hydraulic cutter for cutting metal pipes, reinforcing bars or the like and, more particularly, to a hydraulic cutter having a special type of built-in valve mechanism.
Hydraulic cutters which are easy to carry and handle for cutting reinforcing bars, metal pipes or the like at the construction site have been developed. For example, a hydraulic cutter is known wherein a pump mechanism for forcibly feeding oil from an oil tank is disposed inside a casing main body of the cutter containing the oil tank, and the compressed oil from this pump mechanism is fed to a cylinder to slide a piston head slidably disposed inside the cylinder, thereby linearly displacing a piston rod formed integral with the piston head for performing a cutting operation with a cutting blade mounted at the front end of the piston rod (U.S. Pat. No. 3,733,699).
In this conventional hydraulic cutter, a valve mechanism is incorporated for releasing the compressed oil fed to the cylinder to withdraw the piston head and the piston rod. However, this valve was incorporated at a position shifted from the axis of the piston head. This construction led to various defects. For example, the processing of the piston head was difficult, the precision of the processing was inferior, and the cylinder space for enclosing the valve mechanism had to be made greater. Furthermore, in order to obtain stable and balanced flow of oil, two valve mechanisms are frequently incorporated so that the construction disadvantageously becomes complex and the manufacturing cost becomes high.